1. Field of the Invention
The present invention relates to a system for determining or specifying the status of a number of tasks when one of the tasks is stopped. More specifically, the present invention relates to such a system wherein multiple tasks are assigned to multiple CPU's (central processing units) on a one-to-one basis in a tightly-coupled multiprocessor arrangement which is provided with a plurality of CPU's sharing a single memory.
The present invention is particularly directed to debugging and/or evaluating user's programs to be executed by a parallel machine of SIMD (Single-Instruction stream Multiple-Data stream) type.
2. Description of the Prior Art
In order to speed the execution of a user's program, one known approach is to use a multitasking technique wherein tasks are assigned to a plurality of CPU's on a one-to-one basis and are executed in parallel thereby.
When a user's program is to be debugged and/or evaluated in the above-mentioned multitasking system, it is necessary, when one task is stopped, to suspend or temporarily stop the other tasks in order to examine the status of each of the other tasks.
According to a conventional method, debugging and/or evaluation of a user's program is implemented by means of software only. More specifically, in the event that one task is stopped, the CPU dedicated thereto initiates to execute an interrupt control program of the stopped task and suspends the other tasks through the use of software. After discontinuing the other tasks, each status thereof is examined.
As mentioned above, since the suspending operation of each of the other tasks is carried out only through software, the known method has inherently encountered a problem in that a considerable period of time is required to subsequently suspend the other tasks after one of the same has been stopped. This means that the other tasks continue to be undesirably executed for a relatively long period following the stoppage of one of the tasks, and hence the statuses of the other tasks are unable to be observed exactly.